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The frequency of gamma delta + T cells in the peripheral blood of 26 Turkish, 24 Swedish, 35 Japanese and 14 "Asian' (non-Japanese) healthy blood donors and healthy volunteers were investigated by flow cytometry. In the Turkish group, 9.3% (median value) of the CD3+ peripheral blood T cells expressed the gamma delta T cell receptor. A similar level of gamma delta + T cells was found in the non-Japanese "Asian' healthy volunteers (9.2%), while significantly lower values were detected in the Swedish (4.2%) and Japanese (4.5%) groups. These dramatic differences in normally occurring gamma delta + T cells in different groups of healthy individuals were further reflected by a low incidence of > 10% gamma delta + T cells in the Swedish (0/24) and Japanese (6/35) groups compared to the Turkish (12/26) and "Asian' (5/14) groups. The described gamma delta + T cell differences between distinct ethnic groups are thus likely to be a consequence of environmental factors, but additional genetic influences cannot be ruled out. The present study demonstrates the potential importance of the ethnic origin and environmental history of subjects examined in studies of gamma delta + T cells-disease relations.

We have previously analysed the T-cell receptor (TCR) V-gene usage in peripheral blood T lymphocytes from a group of healthy Scandinavians, and described a biased representation (i.e. a statistically significant higher median representation) for some of the TCR V genes towards the CD4+ subpopulation. In a subsequent study the usage of the same V genes was analysed in single positive (CD4+ CD8- and CD4- CD8+) human thymocytes, and a similar type of skewness was noted. These observations might be explained by an influence of the specificity of the TCR of thymocytes on the maturation into the CD4+ or the CD8+ lineage. Such a model would assume an interaction between a common determinant on the major histocompatibility complex (MHC) class I or class II molecules, or with a peptide that is preferentially presented by either of the two molecules, and the TCR on the maturing thymocyte. To investigate the possible influence of a different genetic background and environment on skewed TCR V-gene representation, we have in this study analysed the TCR V-gene usage in peripheral blood and umbilical cord blood lymphocytes obtained from Asians, with a different ethnic and environmental background from our previous Scandinavian subjects. In the umbilical cord blood lymphocytes the TCR V-gene usage was close to identical between the two different ethnic groups in both CD4+ and CD8+ subpopulations. Analysing the peripheral blood lymphocyte (PBL) TCR V-gene usage, we found that three of the four monoclonal antibodies (MoAb) with a biased reactivity towards the CD4+ subpopulation in the Scandinavian group also showed a similar skewed reactivity in this study. Thus, the majority of the TCR V genes were used in a similar way. Some minor but definite discrepancies could be detected when comparing TCR V-gene usage in adult individuals from these two different ethnic groups. These differences could be inferred to be due to selective peripheral expansion through environmental pressure of T cells utilizing a specific V beta gene segment. We conclude that a striking preservation of biased TCR V-gene usage does exist in humans of distinctly different ethnic origin.